Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. and U.S. Pat. No. 5,146,215 to Drori. The remote transmitter may be used to arm and disarm the vehicle security system or provide other remote control features from a predetermined range away from the vehicle. Also related to remote control of a vehicle function, U.S. Pat. No. 5,252,966 to Lambropoulous et al. discloses a remote keyless entry system for a vehicle. The keyless entry system permits the user to remotely open the vehicle doors or open the vehicle trunk using a small handheld transmitter.
In addition to providing an alarm indication, certain prior art security systems also provide a pre-warning indication which has a lesser volume or shorter duration than the alarm indication. The pre-warning indication is generally triggered by a sensed security threat level that is below a high security threat level needed to trigger the alarm indication. These high and low threat levels may be sensed using a two-stage shock sensor, for example.
The pre-warning feature is particularly advantageous for warning someone who comes too close to, or makes contact with, the vehicle that the vehicle has a security system that can trigger a much more conspicuous alarm indication. Accordingly, if a would-be burglar bumps a vehicle window in an attempt to pick the door lock, a pre-warning indication is triggered to inform the perpetrator that breaking the window or opening the door will result in an alarm indication, and possibly other countermeasures as well.
Many vehicles currently include a keyless entry system, but not an alarm system that provides an alarm based upon sensed threats to the vehicle (i.e., a shock to a window, etc.). Moreover, certain vehicle alarm systems only have single-stage sensor inputs and thus do not provide any pre-warn features. That is, these alarm systems are designed to respond only to a high security threat level and, thus, only provide an alarm indication. Accordingly, to provide a pre-warn indication in a vehicle that already has one of these systems, the only way currently available to do so is to replace the system with one that is designed to provide such functionality. This may be cost prohibitive for many vehicle owners.